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                                <div id="anchor-navigation-ex-navbar"><i class="fa fa-navicon"></i><ul><li><span class="title-icon "></span><a href="#overview"><b>1. </b>Overview</a></li><ul><li><span class="title-icon "></span><a href="#going-back-in-time"><b>1.1. </b>Going back in time</a></li><li><span class="title-icon "></span><a href="#why-you-need-kubernetes-and-what-is-can-do"><b>1.2. </b>Why you need Kubernetes and what is can do</a></li><li><span class="title-icon "></span><a href="#what-kubernetes-is-not"><b>1.3. </b>What Kubernetes is not</a></li><li><span class="title-icon "></span><a href="#whats-next"><b>1.4. </b>What&apos;s next</a></li></ul></ul></div><a href="#overview" id="anchorNavigationExGoTop"><i class="fa fa-arrow-up"></i></a><h1 id="overview"><a name="overview" class="anchor-navigation-ex-anchor" href="#overview"><i class="fa fa-link" aria-hidden="true"></i></a>1. Overview</h1>
<p>Kubernetes is a portable, extensible, open source platform for managing containerized workloads
and services, that facilitates both declarative configuration and automation. It has a large,
rapidly growing ecosystem. Kubernetes services, support, and tools are widely available.</p>
<h2 id="going-back-in-time"><a name="going-back-in-time" class="anchor-navigation-ex-anchor" href="#going-back-in-time"><i class="fa fa-link" aria-hidden="true"></i></a>1.1. Going back in time</h2>
<p><img src="../../../images/kubernetes_en/deployment_era.svg" alt="deployment_era.svg"></p>
<blockquote>
<p>Traditional deployment era</p>
</blockquote>
<p>Early on, organizations ran applications on physical servers. There was no way to define resource
boundaries for applications in a physical server, and this caused resource allocation issues.
For example, if multiple applications run on a physical server, there can be instances where one
application would take up most of the resources, and as a result, the other applications would
underperform. A solution for this would be to run each application on a different physical server.
But this did not scale as resources were underutilized, ad it was expensive for organizations
to maintain many physical servers.</p>
<blockquote>
<p>Virtualized deployment era</p>
</blockquote>
<p>As a solution, virtualization was introduced. It allows you to run multiple Virtual Machines(VMs)
on a single physical server&apos;s CPU. Virtualization allows applications to be isolated between VMs and
provides a level of security as the information of one application cannot be freely accessed by
another application.</p>
<p>Virtualization allow better utilization of resource in a physical server and allows better scalability
because an application can be added or updated easily, reduces hardware costs, and much more.
With virtualization, you can present a set of physical resources as a cluster of disposable
virtual machines.</p>
<blockquote>
<p>Container deployment era</p>
</blockquote>
<p>Containers are similar to VMs, but they have relaxed isolation properties to share the Operating
System (OS) among the applications. Therefore, containers are considered lightweight.
Similar to VM, a container has its own filesystem, share of CPU, memory, process space, and more.
As they are decoupled from the underlying infrastructure, they are portable across clouds
and OS distributions.</p>
<p>They provide extra benefits, such as:</p>
<ul>
<li>Agile application creation and deployment: increased ease and efficiency of container images creation
compared to VM image use.</li>
<li>continuous development, integration, and deployment: provides for reliable and frequent container image
build and deployment with quick and efficient rollbacks (due to image immutability).</li>
<li>Dev and Ops separation of concerns: create application container images at build/release time rather
than deployment time, thereby decoupling applications from infrastructure.</li>
<li>Observability: not only surfaces OS-level information and metrics, but also application health and
other signals.</li>
<li>Environmental consistency across development, testing, and production: runs the same on a laptop as it
does in the cloud.</li>
<li>Cloud and OS distribution portability: runs on Ubuntu, RHEL, CoreOS, on-premises, on major public clouds,
and anywhere else.</li>
<li>Application-centric management: raises the level of abstraction from running an OS on virtual hardware
to running an application on an OS using logical resources.</li>
<li>Loosely, coupled, distributed, elastic, liberated microservices: applications are broken into smaller,
independent pieces and can be deployed and managed dynamically - not be monolithic stack running on one
big single-purpose machine.</li>
<li>Resource isolation: predictable application performance.</li>
<li>Resource utilization: high efficiency and density.</li>
</ul>
<h2 id="why-you-need-kubernetes-and-what-is-can-do"><a name="why-you-need-kubernetes-and-what-is-can-do" class="anchor-navigation-ex-anchor" href="#why-you-need-kubernetes-and-what-is-can-do"><i class="fa fa-link" aria-hidden="true"></i></a>1.2. Why you need Kubernetes and what is can do</h2>
<p>Containers are a good way to bundle and run your applications. In a production environment, you need to
manage th containers that run the applications and ensure that there is no downtime. For example, if a
container goes down, another container needs to start. Wouldn&apos;t it be easier if this behavior was handled
by a system?</p>
<p>That&apos;s how kubernetes comes to rescue! Kubernetes provides you with a framework to run distributed systems
resiliently. It takes care of scaling and failover for your application, provides deployment patterns, and
more. For example: Kubernetes can easily manage a canary deployment for your system.</p>
<p>Kubernetes provides you with:</p>
<ul>
<li>Service discovery and load balancing: Kubernetes can expose a container using the DNS name or using
their own IP address. If traffic to a container is high, Kubernetes is able to load balance and distribute
the network traffic so that the deployment is stable.</li>
<li>Storage orchestration: Kubernetes allows you to automatically mount a storage system of your choice,
such as local storages, public cloud providers, and more.</li>
<li>Automated rollouts and rollbacks: You can describe the desired state for your deployed containers
using Kubernetes, and it can change the actual state to the desired stata at a controlled rate.
For example, remove existing containers and adopt all their resources to the new container.</li>
<li>Automatic bin packing: You provide kubernetes with a cluster of nodes that ic can use to run containerized
tasks. You tell Kubernetes how much CPU and memory (RAM) each container needs. Kubernetes can fit
containers onto your nodes to make the best use of your resources.</li>
<li>Self-healing: Kubernetes restarts containers that fail, replaces containers, kills containers that
don&apos;t respond to your user-defined health check, and doesn&apos;t advertise them to clients until they
are ready to serve.</li>
<li>Secret and configuration management: Kubernetes lets you store and manage sensitive information,
such as passwords, OAuth tokens, and SSH keys. You can deploy and update secrets and application
configuration without rebuilding your container images, and without exposing secrets in your stack configuration.</li>
<li>Batch execution: In addition to services, Kubernetes can manage your batch and CI workloads, replacing
containers that fail, if desired.</li>
<li>Horizontal scaling: Scale your application up and down with a simple command, with a UI, or automatically
based on CPU usage.</li>
<li>IPv4/IPv6 dual-stack: Allocation of IPv4 and IPv6 address to Pods and Services.</li>
<li>Designed for extensibility: Add features to your Kubernetes cluster without changing upstream source code.</li>
</ul>
<h2 id="what-kubernetes-is-not"><a name="what-kubernetes-is-not" class="anchor-navigation-ex-anchor" href="#what-kubernetes-is-not"><i class="fa fa-link" aria-hidden="true"></i></a>1.3. What Kubernetes is not</h2>
<p>Kubernetes is not traditional, all-inclusive PaaS (Platform as a Service) system. Since Kubernetes
operates at the container level rather than at the hardware level, it provides some generally applicable
features common to PaaS offerings, such as deployment, scaling, load balancing, and lets users integrate
their logging, monitoring, and alerting solutions. However, Kubernetes is not monolithic, and these
default solutions are optional and pluggable. Kubernetes provides the building blocks for building
developer platforms, but preserves user choice and flexibility where it is important.</p>
<p>Kubernetes:</p>
<ul>
<li>Does not limit the types of applications supported. Kubernetes aims to support an extremely diverse
variety of workloads, including stateless, stateful, and data-processing workloads. If an application
can run in a container, it should run great on Kubernetes.</li>
<li>Does not deploy source code and does not build your application. Continuous Integration, Delivery, and
Deployment (CI/CD) workflows are determined by organization cultures and preferences as well as
technical requirements.</li>
<li>Does not provide application-level services, such as middleware (for example, message buses),
data-processing frameworks (for example, Spark), database (for example, MySQL), caches,
nor cluster storage systems (for example, Ceph) as built-in services. Such components can run on
Kubernetes, and/or be accessed by applications running on Kubernetes though portable mechanisms,
such as the Open Service Broker.</li>
<li>Does not dictate logging, monitoring, or alerting solutions. It provides some integrations as proof
of concept, and mechanisms to collect and export metrics.</li>
<li>Does not provide mandate a configuration language/system (for example, Jsonnet). It provides a
declarative API that may be targeted by arbitrary forms of declarative specifications.</li>
<li>Does not provide nor adopt any comprehensive machine configuration, maintenance, management,
or self-healing systems.</li>
<li>Additionally, Kubernetes is not a mere orchestration system. In fact, it eliminates the need for
orchestration. The technical definition of orchestration is execution of a defined workflow:
first do A, then B, then C. In contrast, Kubernetes comprises a set of independent, composable
control processes that continuously drive the current state towards provided desired state. It
shouldn&apos;t matter how you get from A to C. Centralized control is also not required. This results
in a system that is easier to use and more powerful, robust, resilient, and extensible.</li>
</ul>
<h2 id="whats-next"><a name="whats-next" class="anchor-navigation-ex-anchor" href="#whats-next"><i class="fa fa-link" aria-hidden="true"></i></a>1.4. What&apos;s next</h2>
<ul>
<li>Take a look at the <a href="components.html#kubernetes-components">Kubernetes Components</a></li>
<li>Take a look at the The Kubernetes API</li>
<li>Take a look at the Cluster Architecture</li>
<li>Ready to Get Started?</li>
</ul>

                                
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